Dense-gas fractionation of mixtures of petroleum macromolecules

Edwards, William F.; Thies, Mark C.

doi:10.1016/j.fluid.2004.08.004

Cited by 5 publications

(4 citation statements)

References 11 publications

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“…7, 2012 a mild formation of radical cations of polycyclic aromatic molecules, preventing unwanted fragmentation. 33,[37][38][39]41 According to Edwards et al, 33 the content of the matrix/pitch used in their study did not significantly affect the results. Thus, we chose the ratio 1:5 (analyte:matrix), the lowest studied.…”

Section: Sample Preparationmentioning

confidence: 76%

“…These results are in accordance with those previously reported by Edwards and Thies. 38,39,41 The results from Marzec 45 also showed a bimodal distribution of masses for coal, with regions between m/z 130-600 and 1300-3500.…”

Section: Studies By Maldi-tof-msmentioning

confidence: 89%

“…Former studies [36][37][38][39][40] suggest that when compounds, to be identified by MALDI, present problems with solubility, miscibility or segregation during crystallization, a matrix should be mixed with the analyte in the solid state with subsequent application, directly or in suspension, in the cell equipment (sample holder). Therefore, there were employed two different methods for sample preparation without solvents.…”

Section: Sample Preparationmentioning

confidence: 99%

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Mesophase evolution in heat-treated solid petroleum pitches

Lima¹,

Lima²,

França³

et al. 2012

J. Braz. Chem. Soc.

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Uma combinação de técnicas analíticas foi utilizada para acompanhar a evolução da mesofase em pixes de petróleo em fase sólida. As amostras foram caracterizadas por dessorção a laser assistida por matriz, seguida de espectrometria de massas por tempo de vôo (MALDI-TOF-MS), ressonância magnética nuclear de 13 C ( 13 C NMR) de alto campo, 1 H NMR de baixo campo, ressonância eletrônica de spin (EPR), microscopia ótica polarizada e análise termogravimétrica (TGA). A análise por MALDI-TOF-MS revelou uma distribuição oligomérica de pesos moleculares no pixe: monomérica (m/z 200 a 400), dimérica (m/z 400 a 650), trimérica (m/z 650 a 950) e tetramérica (m/z 950 a 1600), fator essential para a produção de fibras de carbono, bem como outros compósitos de carbono. Estudos de tempo de relaxação (T 1 ) permitiram a observação de duas grandes áreas: a dos aromáticos e a de mesofase. Estes resultados também mostraram que o tempo de aquecimento aumenta a área de mesofase. Através de medidas não destrutivas de 13 C NMR, foram obtidos os conteúdos de carbonos aromáticos e alifáticos, e também o grau de protonação desses carbonos. A microscopia ótica com luz polarizada mostrou as interfaces entre as regiões anisotrópicas e isotrópicas, bem como o processo de coalescência da mesofase. Os resultados obtidos pelas outras técnicas corroboram com os resultados de MALDI-TOF-MS e NMR.A combination of analytical techniques was used to follow the mesophase evolution of petroleum pitches in the solid phase. The samples were characterized by matrix assisted laser desorption and time of flight analysis by mass spectrometry (MALDI-TOF-MS), high field 13 C nuclear magnetic resonance ( 13 C NMR), low field 1 H NMR, electron spin resonance (EPR), polarized optical microscopy and thermogravimetric analysis (TGA). MALDI-TOF-MS revealed an oligomeric distribution of molecular weights in the pitch: monomeric (m/z 200 to 400), dimeric (m/z 400 to 650), trimeric (m/z 650 to 950) and tetrameric (m/z 950 to 1600), an essential factor for the production of carbon fibers, among other advanced composite of carbon. Relaxation time (T 1 ) studies permitted to observe two large areas: the aromatics and the mesophases. These results also showed that the heating time increases the mesophasic area. Also through direct and non-destructive 13 C NMR measurements, we obtained the content of aromatic and aliphatic carbons, as well as the degree of protonation of these carbons. Optical microscopy with polarized light showed the interfaces between the anisotropic and isotropic regions as well as the process of coalescence of mesophase. The results obtained by the other techniques corroborate the MALDI-TOF-MS and NMR results.

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Section: Sample Preparationmentioning

confidence: 76%

Section: Studies By Maldi-tof-msmentioning

confidence: 89%

Section: Sample Preparationmentioning

confidence: 99%

See 1 more Smart Citation

Mesophase evolution in heat-treated solid petroleum pitches

Lima¹,

Lima²,

França³

et al. 2012

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

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“…For sample deposition, the analyte/matrix mixture was deposited onto the MALDI target surface using one of the following two methods: (1) water spotting or (2) smearing with a spatula. With water spotting, 100–200 μL of deionized water are added to the analyte/matrix mixture powder obtained above.…”

Section: Methodsmentioning

confidence: 99%

The effects of molecular weight distribution and sample preparation on matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric analysis of petroleum macromolecules

Kulkarni

Räder

Thies

2011

Rapid Comm Mass Spectrometry

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To date there have been no systematic, quantitative investigations of the effect of sample preparation on the matrix-assisted laser desorption/ionization time-of-flight (MALDI) mass spectrometry response for polydisperse systems. To this end, the interrelationships between sample preparation, analyte molecular weight distribution (MWD) and solubility, and signal response were investigated for mixtures of alkylated polycyclic aromatic hydrocarbon (PAH) oligomers, the constituents of petroleum pitch that serve as precursors for advanced carbon materials. These PAH oligomers served as a useful analyte system for study, as their solvent solubilities decrease significantly with each increasing oligomeric unit. Molecular weight standards consisting of relatively pure dimer and trimer cuts of the starting M-50 petroleum pitch were produced using a dense-gas/supercritical extraction (DGE/SCE) technique and were then used to produce oligomeric mixtures of well-defined composition for study. Both traditional, solvent-based and newer, solvent-free sample preparation methods were evaluated, and their effects on both homogeneity and signal response were determined. While solvent-free sample preparation methods produced homogeneous samples and reproducible results regardless of the MWD of the analyte, solvent-based samples that contained more than one oligomeric cut produced non-homogeneous samples and poor reproducibilities. The differing solubilities of dimer, trimer, and tetramer oligomers in a given solvent (e.g., CS(2) or toluene) were found to be the cause of the inhomogeneities observed in solvent-based sample preparation. A quantitative analysis study performed with dimer/trimer mixtures over a wide range of compositions via solvent-free sample preparation indicates that linear, reproducible calibration curves can be generated and used to calculate the molecular composition of unknown dimer/trimer mixtures with confidence.

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Fractionation of pitches by molecular weight using continuous and semibatch dense-gas extraction

Edwards

Thies

2006

Carbon

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Dense-gas fractionation of mixtures of petroleum macromolecules

Cited by 5 publications

References 11 publications

Mesophase evolution in heat-treated solid petroleum pitches

Mesophase evolution in heat-treated solid petroleum pitches

The effects of molecular weight distribution and sample preparation on matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric analysis of petroleum macromolecules

Fractionation of pitches by molecular weight using continuous and semibatch dense-gas extraction

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